Structure evolution from Fe2Ni MIL MOF to carbon confined O-doped FeNi/FeF2 via partial fluorination for improved oxygen evolution reaction

Carbon confined active phase plays a significant role in the novel catalyst materials development and fabrication. Herein, we demonstrate such a catalyst material in the form of carbon confined iron-nickel alloy/iron fluoride doped by oxygen (C/O-FeNi/FeF2) derived from the Fe2Ni MIL MOF via facile carbonization and fluorination for efficient oxygen evolution reaction (OER) in the water-splitting reaction. The structural transformation from the Fe2Ni MIL MOF to the C/O-FeNi/FeF2 is demonstrated by the spectroscopic analysis and correlated to their electrochemical catalytic performance. Because of some combined merits resulting from the carbon confined active phase, increased polarity, strong electronic effect and efficient synergism of metal and metal fluoride for the facile active phase reconstruction in this hybrid system, this catalyst exhibits many good characteristics for electrochemical measurements in terms of improved conductivity, high intrinsic activity and stability, fast catalytic kinetics, increase surface area and rapid charge transfer ability. Specifically, the C/O-FeNi/FeF2 catalysts have a low overpotential of ca. 250 mV when loaded on a glass carbon electrode to offer the current density of 10 mA cm−2 in the alkaline electrolyte for OER; and no obvious performance decay is observed in the long-term stability test conducted at different potentials. The current results will be instructive for novel carbon confined catalyst and MOF derived catalyst design and fabrication in the energy catalysis reaction.